1. Field of the Invention
This invention relates generally to laser pointer-tracker systems and particularly to point-ahead laser pointer-tracker systems.
2. Description of the Related Art
Presently known prior art systems employing shared apertures do not provide any way to sense the wavefront corrections needed in both the transmit and receive directions. There is no local beam in the direction of the received target image, so any wavefront correction on the target image either has to use the dim target image itself to sense the needed corrections, or else it is assumed that the target image direction corrections are the same as those in the transmitted, point-ahead, directions.
In direct (non-point-ahead) systems, the transmit and receive directions are the same, so that a local beam aligned in the transmit direction is also aligned with the received target image and can be used for sensing the wavefront corrections needed in the received direction.
Presently known prior art systems employing a stable platform use only a single marker beam aligned in the transmit direction. When applied to a point-ahead system in which this marker beam is driven in the point-ahead direction to point the transmitter laser, the single stable beam will only stabilize the transmitted laser beam and the common path. It does not stabilize the tracker image against jitters in the tracker-marker leg or against what the shared aperture component may do to the tracker-marker leg that it does not do to the common path.
There is no presently known prior art directed to separate aperture, stable platform, point-ahead laser transmitters. Presently known prior art systems of the separate aperture type have been direct pointing (not point-ahead), and, as noted above, point-ahead prior art has been of the shared aperture type.